Impact of Asteroid Defence: Is it worth it?
Asteroid impacts are very bad, if the asteroid is big enough or is going fast enough. We should be able to defend against one, if we happen to find that one is coming toward us.
But defence against possible asteroid strikes will be very expensive since the BIGGEST problem is finding when one is coming in to hit us. The effort to find “dangerous” asteroids will probably involve fielding many space telescopes (to chart as many asteroids as possible–both those in a “near Earth orbit” as well as those in orbits which “swoop in” from the outer reaches of the Solar System). (To say nothing about watching for the kind of object that is generally speculated as having smashed/gouged the Moon out of the early Earth: “Loose” planetoids [and “Brown Dwarfs”?] which do not belong to any stellar system.)
To my mind, the best place to put computerized asteroid-charting space-telescopes would be co-located in the orbit of Mars—far enough out to give PLENTY of warning time and available to management/supervision from a human-based establishment on one of Mars’ moons (Phobos or Demos), or even on Mars, itself. (( Having “cut my alien-fighting teeth” as a cyber-space-ranger based on Phobos… )) Both the automated space-telescopes and the management base (on Mars? Europa?) will be expensive, to say the least.
The impact of the asteroid-charting effort on the economy will be large (due to gravitational interactions, they change orbits not-infrequently so that the effort will be a never-ending project). But should even a single sizable or “too speedy” asteroid hit Earth in a populated area, the consequences will be nearly-unthinkable!
The Question: Is the cost of defending against the not-large chance of the truly hideous consequences of an asteroid strike worth it?